oh dear-

pardon my ignorance but,
class user{
private $user_id;
private $user_name;
public function __construct($user_id) {
$this -> user_id=$user_id;
$this -> user_name = $result['username'];

what is '$this ->'

>>23
Java seriously halfassed every bit of OO. int isn't an object, for example. You can't subclass it, you can't do shit with it. You have to use that stupidass Integer wrapper class and then write everything with fucking verbose function names because Java also doesn't have any sort of operator overriding.

Since half the fucking standard library has totally different methods for everything, and it's all halfassed shit, you can't e.g. pass a TCP connection to a method that's expecting something opened from a file stream and expect it to work sanely. In order to do anything like that you usually have to write a bunch of fucking wrapper classes on top of the standard library to make up for the fact that it sucks dicks.

Try using a proper OO language some time and you'll notice that it's actually not completely hellish to work with. Until then, shut the fuck up about Java being OO, because it's not, it's a pile of monkey shit.